1. Field of the Invention
The present invention relates to a mobile communication terminal, such as a mobile telephone terminal, etc., having a function of transmitting an FM radio wave, for example, and a method of controlling a transmission characteristic thereof.
2. Description of the Related Art
Recently, considerable progress has been made for mobile telephone terminals to have multiple functions. For example, some mobile telephone terminals having a transmitter, such as an FM transmitter, in addition to a transmitter/receiver for connecting to a mobile telephone network are being brought to the market.
Here, in general, a transmission level of a transmitter (FM transmitter, etc.) built in a mobile telephone terminal is specified in a state of a single mobile telephone terminal, that is to say, in a state of not being connected with various kinds of accessory devices, for example such as an earphone, a hands-free set, a battery charger, etc. Specifically, the transmission level is set so that a maximum transmission level is obtained within a range of not violating the Radio Law. Also, a transmission level, a frequency band, further, approval/disapproval of transmission, etc., of the transmitter, such as an FM transmitter, to be mounted on a mobile telephone terminal are set in accordance with a specification of each country.
In this regard, Japanese Unexamined Patent Application Publication No. 2005-160022 (FIG. 1) has disclosed a mobile telephone in which a connector of the mobile telephone is provided with a charging terminal and an antenna connection terminal, an external antenna cable is connected to the connector, and thereby a transmission/reception sensitivity of the mobile telephone has been improved, and charging the mobile telephone has become possible at the same time.